old comp keeps reseting on post.

i got an old Digital Venturis from my brother. the system aperent worked up till about 2 weeks ago. at which time all its drives (hdd/fdd/cd) and its pci cards a nic where removed. i'm looking to turn it in to a fire wall, but im having a problem on the post. as soon as the post screen is done the system reboots an runs the post again. I can seem to get into the bios settings. and there is 2 mesages in the post that i have never see before:

umb upper limit segment address: f52e
140 coprosessor test

the post also says that the system battery is dead. but have'nt been able to fined the old battery or a batery leed.
also i have tryed chageing the memory sticks.

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Old PC's also tend to have several small button-batteries in a shrink-material directly solderd to the mainboard. Seldom that those batteries outlive the mainboard. Look for something that resembles a caterpillar.
When the battery is dead, usually time settings are also lost, so you're asked to supply them.
Y
ou say you hve disconnected fdd, hdd and cd's, so what is there for the system to boot. If there's nothing, it wil stay in the loop. Connect the floppy, and use a dos-bootable floppy, or your firewall-disk.

what exact type is the computer?
It wasn't until the 486 that coprocessors were integrated, up to the 386 you could install a separate co-processor.